Ray Kurzweil - How to Create a Mind - The Secret of Human Thought Revealed

From the midbrain, sensory information then flows through a nut-sized region called the posterior ventromedial nucleus (VMpo) of the thalamus, which computes complex reactions to bodily states such as “this tastes terrible,” “what a stench,” or “that light touch is stimulating.” The increasingly processed information ends up at two regions of the neocortex called the insula. These structures, the size of small fingers, are located on the left and right sides of the neocortex. Dr. Arthur Craig of the Barrow Neurological Institute in Phoenix describes the VMpo and the two insula regions as “a system that represents the material me.” 4

The sensory-touch pathway in the brain.

Among its other functions, the thalamus is considered a gateway for preprocessed sensory information to enter the neocortex. In addition to the tactile information flowing through the VMpo, processed information from the optic nerve (which, as noted above, has already been substantially transformed) is sent to a region of the thalamus called the lateral geniculate nucleus, which then sends it on to the V1 region of the neocortex. Information from the auditory sense is passed through the medial geniculate nucleus of the thalamus en route to the early auditory regions of the neocortex. All of our sensory data (except, apparently, for the olfactory system, which uses the olfactory bulb instead) passes through specific regions of the thalamus.

The most significant role of the thalamus, however, is its continual communication with the neocortex. The pattern recognizers in the neocortex send tentative results to the thalamus and receive responses principally using both excitatory and inhibitory reciprocal signals from layer VI of each recognizer. Keep in mind that these are not wireless messages, so that there needs to be an extraordinary amount of actual wiring (in the form of axons) running between all regions of the neocortex and the thalamus. Consider the vast amount of real estate (in terms of the physical mass of connections required) for the hundreds of millions of pattern recognizers in the neocortex to be constantly checking in with the thalamus. 5

So what are the hundreds of millions of neocortical pattern recognizers talking to the thalamus about? It is apparently an important conversation, because profound damage to the main region of the thalamus bilaterally can lead to prolonged unconsciousness. A person with a damaged thalamus may still have activity in his neocortex, in that the self-triggering thinking by association can still work. But directed thinking—the kind that will get us out of bed, into our car, and sitting at our desk at work—does not function without a thalamus. In a famous case, twenty-one-year-old Karen Ann Quinlan suffered a heart attack and respiratory failure and remained in an unresponsive, apparently vegetative state for ten years. When she died, her autopsy revealed that her neocortex was normal but her thalamus had been destroyed.

In order to play its key role in our ability to direct attention, the thalamus relies on the structured knowledge contained in the neocortex. It can step through a list (stored in the neocortex), enabling us to follow a train of thought or follow a plan of action. We are apparently able to keep up to about four items in our working memory at a time, two per hemisphere according to recent research by neuroscientists at the MIT Picower Institute for Learning and Memory. 6 The issue of whether the thalamus is in charge of the neocortex or vice versa is far from clear, but we are unable to function without both.

Each brain hemisphere contains a hippocampus, a small region that looks like a sea horse tucked in the medial temporal lobe. Its primary function is to remember novel events. Since sensory information flows through the neocortex, it is up to the neocortex to determine that an experience is novel in order to present it to the hippocampus. It does so either by failing to recognize a particular set of features (for example, a new face) or by realizing that an otherwise familiar situation now has unique attributes (such as your spouse’s wearing a fake mustache).

The hippocampus is capable of remembering these situations, although it appears to do so primarily through pointers into the neocortex. So memories in the hippocampus are also stored as lower-level patterns that were earlier recognized and stored in the neocortex. For animals without a neocortex to modulate sensory experiences, the hippocampus will simply remember the information from the senses, although this will have undergone sensory preprocessing (for example, the transformations performed by the optic nerve).

Although the hippocampus makes use of the neocortex (if a particular brain has one) as its scratch pad, its memory (of pointers into the neocortex) is not inherently hierarchical. Animals without a neocortex can accordingly remember things using their hippocampus, but their recollections will not be hierarchical.

The capacity of the hippocampus is limited, so its memory is short-term. It will transfer a particular sequence of patterns from its short-term memory to the long-term hierarchical memory of the neocortex by playing this memory sequence to the neocortex over and over again. We need, therefore, a hippocampus in order to learn new memories and skills (although strictly motor skills appear to use a different mechanism). Someone with damage to both copies of her hippocampus will retain her existing memories but will not be able to form new ones.

University of Southern California neuroscientist Theodore Berger and his colleagues modeled the hippocampus of a rat and have successfully experimented with implanting an artificial one. In a study reported in 2011, the USC scientists blocked particular learned behaviors in rats with drugs. Using an artificial hippocampus, the rats were able to quickly relearn the behavior. “Flip the switch on, and the rats remember. Flip it off and the rats forget,” Berger wrote, referring to his ability to control the neural implant remotely. In another experiment the scientists allowed their artificial hippocampus to work alongside the rats’ natural one. The result was that the ability of the rats to learn new behaviors strengthened. “These integrated experimental modeling studies show for the first time,” Berger explained, “that…a neural prosthesis capable of real-time identification and manipulation of the encoding process can restore and even enhance cognitive mnemonic processes.” 7 The hippocampus is one of the first regions damaged by Alzheimer’s, so one goal of this research is to develop a neural implant for humans that will mitigate this first phase of damage from the disease.

There are two approaches you can use to catch a fly ball. You could solve the complex simultaneous differential equations controlling the ball’s movement as well as further equations governing your own particular angle in viewing the ball, and then compute even more equations on how to move your body, arm, and hand to be in the right place at the right time.

This is not the approach that your brain adopts. It basically simplifies the problem by collapsing a lot of equations into a simple trend model, considering the trends of where the ball appears to be in your field of vision and how quickly it is moving within it. It does the same thing with your hand, making essentially linear predictions of the ball’s apparent position in your field of view and that of your hand. The goal, of course, is to make sure they meet at the same point in space and time. If the ball appears to be dropping too quickly and your hand appears to be moving too slowly, your brain will direct your hand to move more quickly, so that the trends will coincide. This “Gordian knot” solution to what would otherwise be an intractable mathematical problem is called basis functions, and they are carried out by the cerebellum, a bean-shaped and appropriately baseball-sized region that sits on the brain stem. 8